When Ron Gordon, a mathematics teacher, was writing down the date 9 September, 1981, he realised that there was a curious feature about the numbers in it – 9/9/81 — ‘81’ was the product of 9 squared, 9 was the square root of 81.

There are only nine Square Root Days in every century

Gordon realised that only nine dates in every century shared a similar attribute and he designated such days “Square Root Days”.

Today — 4/4/16 — is Square Root Day. The previous Square Root Day was observed on 3/3/09, while the one after this will occur on 5 May, 2025 (5/5/25).

Lest you think that solving some math problems is the only way to celebrate Square Root Day, Gordon has other ideas. According to him, you can “form a large square root sign, have root beer in square glasses, feed a poor person a square meal, travel by a bus route that is a square root, anything”. Those who come up with the most innovative way to celebrate will win $18 each (a total of $441.6 distributed among 4+4+16 people, i.e. 24 winners).